Chemistry of ketene acetals IV. A simple and general method for the preparation of 4-hydroxy-γ-butyrolactones and 2-butenolides from 1,1-dimethoxypropene and α-acyloxy aldehydes and ketones

✍ Scribed by R. W. Aben; R. Hofstraat; J. W. Scheeren

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 494 KB
• Volume: 100
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19811001003

✦ Synopsis

Abstract

α‐Acyloxy aldehydes (2a,b) react with 1,1‐dimethoxypropene (1) in the presence of ZnCl~2~ to yield 2,2‐dimethoxy‐3‐methyloxetanes (3a,b). Stronger electron‐withdraxing acyl groups are necessary for the analogous conversion ofα‐acyloxy ketones (2c,d,e). Hydrolysis of the acyloxy group with potassium hydroxide yields the corresponding hydroxyoxetanes (4) which rearrange under neutral or weakly acidic conditions to 2,2‐dimethoxy‐3‐methyl‐4‐hydroxytetrahydrofurans (5). By mild acidic hydrolysis of 5, the corresponding γ‐butyrolactores (6) are obtained in moderate to good yields. Treatment of 6 with concentrated sulfuric acid yields 3‐methyl‐2‐(5H)‐furanones (3‐methylbutenolides, 10).